The Opera House seems to have shimmered on Bennelong Point forever. Most Sydney-siders think of it like the late summer southerly, as an unchanging and essential part of their city...

...A testament to the architect's art, as natural as the harbour it adorns and a miracle twice over.

Firstly, because the parochial Australia of the 1950s managed to find then choose, Jorn Utzon's design.

And secondly, because Utzon himself managed to discover a way of constructing the shells of the Opera House that was startling in its architectural elegance.

The controversy surrounding its construction is well known.

Utzon was forced out mid-way through the project, leaving the building's interiors to be finished by others ... not one of Australia's finest moments.

But this week marks the Opera House's 25th anniversary, so tonight we'll celebrate the birthday of Utzon's great gift to our nation with three leading architects.

And if a great building is one which is infinitely suggestive to the eye ... Always throwing up new ways of looking at it ... Then the tape piece we are about to watch proclaims the Opera House to be such a building.

It was produced by Bronwen Reid and Brett Evans ... The narrator is Jennifer Taylor, adjunct professor of architecture at the Queensland University of Technology.

In a moment we'll talk with two of Australia's leading architects ... But our first guest is Renzo Piano...one of the worlds acclaimed architects..

... Last year he received the Pritzker Architecture Prize - often described as the 'Nobel prize' for architects.

He has designed some of the world's most highly regarded buildings ... Including the Pompidou Centre in Paris, the Tjiboau Cultural Centre in New Caledonia, and the renovation of Berlin's Postdammer Platz.

A building of his design ... on a site in Sydney's Macquarie Street ... just 800 metres up the road from the Opera House ... is currently under construction.

And now to our other guests...both of them in the galaxy of Australian architectural stars.

Glenn Murcutt...who's done for corrugated iron what the Greeks did for columns...in 1992 he received the prestigious Alvar Aalto medal from Finland.

..And Ken Maher....the managing principal of the architectural firm, Hassell. He led the design team responsible for the Olympic Park rail station which was recently presented with the Sir Zelman Cowan award for public building.